Centrifugal devices for distributing blood specimens over display surfaces are well known. In the most common form, they include a means for positioning and holding a microscope slide on which a blood sample is placed. The slide is then spun about at high speed to achieve the desired placement of the blood.
This invention relates to a process, and apparatus useful therein, for distributing blood on, say, a glass slide for subsequent inspection with a microscope. Such distribution is often referred to as "filming " by those working in medical laboratories.
There are a number of problems associated with the distribution of a blood sample on a glass slide. Perhaps the most obvious problem is that of obtaining an even distribution over the entire slide. The usual manual method consists of placing a drop of blood on the slide and then using a second slide to smear the blood along the slide. This technique usually results in poor lateral distribution, and the excessively narrow smear along the slide usually consists of excessively thick and ultrathin areas. To avoid such problems, centrifugal equipment was introduced which utilized centrifugal force to spread blood along the length of a spinning slide and utilized the acceleration of the slide to achieve a lateral distribution of the blood.
The centrifugal procedure is a substantial advance in the art, especially as practiced with apparatus disclosed in commonly-owned and copending U.S. Pat. application Ser. No. 469,099 filed May 13, 1974 by Barger and Holroyd. In that application, apparatus is described wherein a waste-blood receiving means rotates with the blood-specimen bearing slide and collects specimen waste which is thrown off the slide. This apparatus is a very substantial advance over the art; it markedly reduces the potential for air contamination by any disease-bearing airborne waste resulting from operation of centrifugal blood filmers. Nevertheless, when filter paper is taped inside the top cover of a device of the type described in Ser. No. 469,099, it is usually still possible to detect several pin-point sized deposits of blood indicating some undesirable air transport of specimen material. It should be emphasized that the quantity of such material is magnitudes below that experienced with prior art blood filmers; nevertheless, it is desirable to reduce this so-called "aerosol" to as close to zero as can be accomplished. Various changes in the operating conditions and design parameters did not yield a solution to the problem: the "pin-point" contamination persisted.
It was work directed towards finding a means to achieve the reduction of such contamination which was undertaken by the instant inventors. It is the results of such work that are the subject of the instant disclosure.